CN109154047A

CN109154047A - Method for manufacturing the steel plate through replying with austenitic matrix

Info

Publication number: CN109154047A
Application number: CN201780030117.6A
Authority: CN
Inventors: 让-克里斯托夫·埃莱; 尼古拉斯·沙博尼耶; 蒂埃里·永戈; 布朗迪诺·雷米
Original assignee: ArcelorMittal SA
Current assignee: ArcelorMittal SA
Priority date: 2016-05-24
Filing date: 2017-05-23
Publication date: 2019-01-04
Anticipated expiration: 2037-05-23
Also published as: KR101991220B1; KR20180128512A; PL3464666T3; CA3025453A1; WO2017203313A1; MX2018014322A; EP3464666A1; UA123681C2; ZA201806784B; MA45132B1; EP3464666B1; CA3025453C; US20190276910A1; HUE051053T2; JP2021088774A; BR112018072135A2; BR112018072135B1; ES2814002T3; JP7395524B2; JP2019521248A

Abstract

The present invention relates to a kind of methods for producing the steel plate through replying with austenitic matrix with expected mechanical property.

Description

Method for manufacturing the steel plate through replying with austenitic matrix

The present invention relates to a kind of methods for producing the steel plate through replying with austenitic matrix.The present invention is particularly Suitable for manufacturing motor vehicles.

In order to save the weight of vehicle, it is known to use high strength steel is for manufacturing motor vehicles.For example, for structure member Manufacture, it is necessary to improve the mechanical property of such steel.However, although the intensity of steel is improved, the extension of high-carbon steel Rate reduces, and therefore formability can also reduce.In order to overcome these problems, the steel plate through replying is had already appeared, especially It is the twin crystal induction plastic steel (TWIP steel) with good formability.Although product shows extraordinary formability, Mechanical property such as ultimate tensile stress and yield stress may be not high enough and be unable to satisfy automobile application.

In order to improve the intensity of these steel while keeping good machinability, it is known that induced by cold rolling highly dense Then the twin of degree removes dislocation by reply processing but retains twin.

However, there is the risk that cannot obtain expected mechanical property by applying such method.In fact, ability The technical staff in domain can only in accordance with known methods, and whether then measure realizes the phase from the point of view of the mechanical property of steel plate obtained The mechanical property of prestige.Can not the condition of method of adjustment obtain expected mechanical property.

Therefore, the purpose of the present invention is to a kind of show at least one expected mechanical property for manufacturing by providing The method of steel plate through replying solves disadvantages mentioned above, and such mechanical property improved.Another purpose is to provide one kind The steel plate through replying with the mechanical property improved in this way.

The purpose is realized by providing the method according to claim 1 for being used to manufacture TWIP steel plate.This method It can also include the feature of claim 2 to 20.

Another purpose is realized by providing TWIP steel plate according to claim 21.

Other features and advantages of the present invention will be by of the invention described in detail below and become obvious.

Following term will be defined:

- M: mechanical property

-M_Target: the target value of mechanical property,

-M_{Recrystallization}: the mechanical property after recrystallization annealing,

-M_{Cold rolling}: the mechanical property after cold rolling,

- UTS: ultimate tensile strength,

- TE: breaking elongation,

- P:pareq value,

-P_Target: the target value of pareq,

The full width at half maximum (FWHM) of-FWHM:X Ray Diffraction Spectroscopy, and

-FWHM_Target: the target value of the full width at half maximum (FWHM) of X-ray diffraction spectra.

The present invention relates to a kind of method for manufacturing the steel plate through replying with austenitic matrix, the steel plate performance It is equal to or more than target value M out_TargetAt least one mechanical property (M), the composition of the steel plate includes by weight:

0.1% < C < 1.2%,

13.0%≤Mn < 25.0%,

S≤0.030%,

P≤0.080%,

N≤0.1%,

Si≤3.0%,

And on the basis of entirely optional, one or more of elements such as below,

Nb≤0.5%,

B≤0.005%,

Cr≤1.0%,

Mo≤0.40%,

Ni≤1.0%,

Cu≤5.0%,

Ti≤0.5%,

V≤2.5%,

Al≤4.0%,

The remainder of composition is constituted by iron and by the inevitable impurity that exploitation generates,

This method includes being step below:

A. calibration steps, in which:

I. prepare have been subjected to 400 DEG C to 900 DEG C the heat treatment during 40 seconds to 60 minutes described steel at least two Sample, the heat treatment correspond to Pareq value P,

II. X-ray diffraction is carried out to obtain the spectrum including main peak to the sample, measures the main peak in half eminence Width FWHM,

III. the M of such sample is measured,

IV. the reply or recrystallization state of each sample are measured,

V. song of the M as the function of FWMH is drawn in the region that wherein sample is returned to 100% but does not recrystallize from 0 Line,

B. step is calculated, in which:

I. it determines and corresponds to M_TargetFWHM_TargetValue,

II. it determines and carries out to reach such M_TargetHeat treatment pareq value P_Target, and

III. selection corresponds to P_TargetThe time t of value_TargetWith T ° of temperature_Target,

C. there is M_{Recrystallization}Recrystallization steel plate offer step,

D. in order to obtain with M_{Cold rolling}Steel plate cold rolling step, and

E. at T ° of temperature_TargetUnder in time t_TargetThe annealing steps that period carries out.

It is not intended to by any theoretical constraint, it appears that when applying the method according to the invention, annealing steps can be obtained E technological parameter) has the steel plate through replying of expected improved mechanical property, especially TWIP steel plate to obtain.

About the chemical composition of steel, C plays an important role in terms of the formation of microscopic structure and mechanical property.Which increase Stacking fault energy and the stability for promoting austenite phase.It is mixed when with the Mn of content by weight 13.0% to 25% When, carbon content obtains this stability when being 0.5% or higher.There are vanadium carbide, high Mn content can increase Add solubility of the vanadium carbide (VC) in austenite.However, having the C content for being greater than 1.2% due to such as vanadium carbide Or the excess of carboritride is precipitated and causes the risk of ductility reduction.Preferably, carbon content by weight 0.4% to 1.2%, more preferably 0.5% to 1.0% to obtain enough intensity.

Mn is also for improving intensity, for increasing stacking fault energy and for the essential elements of stable austenite phase.Such as Then there is the risk for forming martensitic phase, this is readily apparent that reduce deformability less than 13.0% in its content of fruit.In addition, When manganese content is greater than 25.0%, the formation of twin is suppressed, and therefore, although intensity increases, ductility at room temperature is reduced.It is excellent Selection of land, manganese content are 15.0% to 24.0%, and more preferably 17.0% to 24.0% to optimize stacking fault energy and prevent Martensite is formed under anamorphic effect.In addition, when Mn content is greater than 24.0%, by the deformation pattern of twin not over complete The deformation pattern of perfect dislocation sliding is advantageous.

Al is the particularly effective element of deoxidation to steel.As C, which increase stacking fault energies, and it reduce formation The risk of martensite is deformed, so as to improve ductility and anti-delayed fracture resistance.However, if Al is in the steel with high Mn content It is present in excess, then Al is a disadvantage, because Mn improves solubility of the nitrogen in molten iron.If existed in steel a large amount of Al, the then N combined with Al are precipitated in the form of aln precipitation (AlN), this hindered during thermal transition the migration of crystal boundary and It is readily apparent that increase cracked risk in continuous casting.In addition, as described below, it is necessary to which there have the N of sufficient amount to be thin to be formed Precipitate, substantially carbonitride.Preferably, Al content is less than or equal to 2%.When Al content is greater than 4.0%, there is suppression Make the risk for forming twin and reducing ductility.Preferably, the amount of Al is greater than 0.06% and more preferably larger than 0.7%.

Correspondingly, nitrogen content is necessary for 0.1% or smaller to prevent precipitation and the volume defect (gas of AlN during solidification Bubble) formation.In addition, when in the presence of can be with element (such as vanadium, niobium, titanium, chromium, molybdenum and boron) of nitride form precipitation, nitrogen Content must not exceed 0.1%.

According to the present invention, the amount of V is less than or equal to 2.5%, it is therefore preferable to 0.1% to 1.0%.Preferably, V-arrangement is at precipitation Object.Preferably, volume fraction of such element in steel is 0.0001% to 0.025%.Preferably, the most numerical digit of vanadium In the position in crystal grain.Advantageously, the average-size of vanadium is less than 7nm, it is therefore preferable to 1nm to 5nm and more preferably 0.2nm to 4.0nm.

Silicon is also for making steel-deoxidizing and for the effective element of solid phase hardening.However, being greater than 3% content, silicon is reduced Elongation percentage and during certain assembling process tend to form undesirable oxide, it is therefore necessary to it be made to remain less than the limit System.Preferably, the content of silicon is less than or equal to 0.6%.

Sulphur and phosphorus are the impurity for making embrittlement of grain boundaries.Their own content must not exceed 0.030% and 0.080% to protect Hold enough hot ductilitys.

Some boron can be added, are up to 0.005%, preferably up to 0.001%.The element is segregated simultaneously in grain boundaries And increase their cohesive force.It is not wishing to be bound by theory, it is believed that this causes to subtract by residual stress after compression moulding It is small and preferably anticorrosive under the stress of the component thus shaped.The element is segregated and is increased at austenite grain boundary Their cohesive force.Boron is precipitated for example in the form of boron-carbide and boron nitride.

Nickel can be optionally for the intensity for improving steel by solution hardening.However, for cost reasons etc., it is desirable to it will Nickel content is limited to maximum level and is 1.0% or smaller and is preferably lower than 0.3%.

Similarly, optionally, copper of the addition content no more than 5% is a kind of side by the precipitation-hardening steel of copper metal Formula.However, being greater than the content, copper is the reason of causing the surface defect of the plate of hot rolling to occur.Preferably, the amount of copper is less than 2.0%.Preferably, the amount of Cu is greater than 0.1%.

Titanium and niobium are also can be optionally for the element realizing hardening by forming precipitate and strengthening.However, working as Nb Or Ti content be greater than 0.50% when, exist excessively be precipitated may cause toughness reduction risk, this must be avoided.Preferably, Ti Amount by weight 0.040% to 0.50% or by weight 0.030% to 0.130%.Preferably, Ti content is by weight It is calculated as 0.060% to 0.40% and such as 0.060% to 0.110%.Preferably, the amount of Nb is greater than 0.01% simultaneously by weight And more preferably 0.070% to 0.50% or 0.040% to 0.220%.Preferably, content of niobium is by weight 0.090% to 0.40% and it is advantageously 0.090% to 0.200%.

Chromium and molybdenum may be used as the optional elements of the intensity for improving steel by solution hardening.However, since chromium reduces Stacking fault energy, so its content must not exceed 1.0% and preferably 0.070% to 0.6%.Preferably, chromium contains Amount is 0.20% to 0.5%.Molybdenum can be with 0.40% or smaller amount, preferably 0.14% to 0.40% amount addition.

Furthermore, it is undesirable to theoretical be constrained by any, it appears that vanadium, titanium, niobium, chromium and molybdenum precipitate can reduce lag and open The sensibility split, and do so and will not reduce ductility and property of toughness.It is therefore preferred that selected from carbide, nitride and At least one of titanium, niobium, chromium and the molybdenum of carbonitride form element is present in steel.

According to the present invention, the method includes calibration steps A.I), wherein prepare have been subjected to 400 DEG C to 900 DEG C At least two sample of heat-treated steel plate during 40 seconds to 60 minutes, the sample, the heat treatment correspond to Pareq value P. In this step, determine the parameter for being known as Pareq the different heat treatment of different time can be carried out more at different temperatures, It passes through defined below:

Pareq=-0.67^*log(∫-ΔH/RT)^*dt)

Wherein Δ H: diffusion energy (be equal to 300kJ/mol) of the iron in iron, the temperature of T=circulation integrate as in entire heat It handles on the time.Heat treatment is hotter or more long, and Pareq value is lower.Two different heat treatments with identical Pareq value will be Identical result is provided on identical steel grade.Preferably, Pareq value is greater than 14.2, more preferably 14.2 to 25 and more preferably 14.2 to 18.

Then during the step A.II), X-ray diffraction is carried out to sample to obtain the spectrum including main peak, described in measurement The full width at half maximum (FWHM) FWHM of main peak.X-ray diffraction is a kind of non-destructive analysis technology, is provided brilliant about the inside of crystalline material The details of lattice, the details including unit cell dimension, bond distance, bond angle and site sequence (site-ordering).Directly related It is monocrystalline refine, wherein the data generated by X-ray analysis are explained and refine is to obtain crystal structure.In general, X-ray crystal Be the tool of such crystal structure for identification.According to the present invention, steel plate has austenitic matrix, and austenitic matrix has Face-centered cubic system.It is therefore preferred that the main peak of measurement full width at half maximum (FWHM) FWHM corresponds to Miller indices [311].In fact, recognizing It is the best representative that dislocation density influences for the peak (for the feature of austenite system).

Then, during step A.III), the M of such sample is measured.Preferably, M be ultimate tensile strength (UTS), Breaking elongation (TE) or both (UTS*TE).

After the reply or recrystallization state that measure each sample during step A.IV).Preferably, aobvious with scanning electron Micro mirror (SEM) and EBSD (electron backscatter diffraction) or transmission electron microscope (TEM) measure such state.

Then, during step A.V), M is drawn in the region that wherein sample is returned to 100% but does not recrystallize from 0 The curve of function as FWMH.

According to the present invention, it realizes and calculates step B).Calculating includes step B.I), correspond to M wherein determining_TargetFWHM_Target Value.Preferably, FWHM_TargetGreater than 1.0 ° and it is advantageously 1.0 ° to 1.5 °.

In a preferred embodiment, wherein M is UTS, and the determination of FWHM is realized using following formula:

UTS_Target=UTS_{Cold rolling}-(UTS_{Cold rolling}-UTS_{Recrystallization})^*(exp((-FWHM+2.3)/2.3)-1)⁴)

In that case it is preferable that UTS_TargetMore than or equal to 1430MPa and more preferably 1430MPa extremely 2000MPa。

In another preferred embodiment, wherein M is TE, utilize following formula realize calculate step B.I) during FWHM Determination:

TE_Target=TE_{Cold rolling}-(TE_{Recrystallization}-UTS_{Cold rolling})^*(exp((-FWHM+2.3)/2.3)-1)^2.5)

In that case it is preferable that TE_TargetMore than or equal to 15% and more preferably 15% to 30%.

In another preferred embodiment, wherein M is UTS*TE, is realized using following formula and calculates step B.I) during The determination of FWHM:

UTS_Target ^*TE_Target=100000^*(1-0.5FWHM)

In that case it is preferable that UTS_Target*TE_TargetGreater than 21000 and more preferably 21000 to 60000, TE_TargetIt is up to 30%.

Then, step B.II is carried out), it carries out wherein determining to reach such M_TargetHeat treatment pareq value P_Target。 Preferably, P_TargetGreater than 14.2, more preferably 14.2 to 25 and more preferably 14.2 to 18.

Later, it is realised in that selection corresponds to P_TargetThe time t of value_TargetWith T ° of temperature_TargetStep B.III).Preferably, T°_TargetIt is 400 DEG C to 900 DEG C, t_TargetIt is 40 seconds to 60 minutes.

It then, according to the method for the present invention include that there is M_{Recrystallization}Recrystallization steel plate offer step.In fact it is preferred to Ground, 700 DEG C to 900 DEG C at a temperature of the recrystallization annealing that carries out after steel plate recrystallize.For example, recrystallizing at 10 seconds extremely It is realized during 500 seconds, preferably 60 seconds to 180 seconds.

In a preferred embodiment, when M is UTS, UTS_{Recrystallization}Greater than 800MPa, it is therefore preferable to which 800MPa is extremely 1400MPa and more preferably 1000MPa are to 1400MPa.

In another preferred embodiment, when M is TE, TE_{Recrystallization}Greater than 20%, preferably more than 30% and more Preferably 30% to 70%.

In another preferred embodiment, when M is TE*UTS, TE_{Recrystallization}*UTS_{Recrystallization}Greater than 16000, more preferably Greater than 24000 and it is advantageously 24000 to 98000.

Then, cold rolling step D is realized) there is M to obtain_{Cold rolling}Steel plate.Preferably, reduction ratio is 1% to 50%, preferably Ground 1% to 25% or 26% to 50%.It allows steel thickness to reduce.In addition, can be through according to the steel plate of above method manufacture By by undergoing the strain hardening of the milling step that there is the intensity improved.In addition, the step induces highdensity twin, from And improve the mechanical property of steel plate.

In a preferred embodiment, when M is UTS, UTS_{Cold rolling}Greater than 1000, preferably more than 1200MPa and Be advantageously greater than 1400MPa.

In another preferred embodiment, when M is TE, TE_{Cold rolling}Greater than 2%, more preferably 2% to 50%.

In another preferred embodiment, when M is TE*UTS, TE_{Cold rolling}*UTS_{Cold rolling}Greater than 2000, preferably 2400 And more preferably 2400 to 70000.

Then, in time t_TargetPeriod is at T ° of temperature_TargetIt is lower to carry out annealing steps E).

After the second cold rolling, hot dip coating step G can be carried out).Preferably, step G) using based on aluminium bath or be based on The bath of zinc is realized.

In a preferred embodiment, hot-dip step is carried out using the bath based on aluminium comprising following component: small Si in 15%, the Fe less than 5.0%, optionally 0.1% to 8.0% Mg and optionally 0.1% to 30.0% Zn, it is remaining Part is Al.

In another preferred embodiment, hot-dip step is carried out with the bath based on zinc comprising following component: 0.01% to 8.0% Al, optionally 0.2% to 8.0% Mg, remainder Zn.

Liquid-bath can also be comprising from providing ingot or the inevitable impurity passed through from steel plate in liquid-bath and residual Remaining element.For example, optional impurity is selected from Sr, Sb, Pb, Ti, Ca, Mn, Sn, La, Ce, Cr, Zr or Bi, every kind of other element Content by weight be lower than 0.3 weight %.The residual elements passed through from offer ingot or from steel plate in liquid-bath can Think that content is up to 5.0 weight %, the preferably iron of 3.0 weight %.

For example, annealing steps can be carried out after coating deposition to obtain the steel plate through zinc-plated diffusion annealing.

Therefore, the tool at least one expection and improved mechanical property is obtained by application according to the method for the present invention There is the steel plate through replying of austenitic matrix.

Embodiment

In this embodiment, using the steel plate formed with following weight:

C (%)	Mn (%)	Si (%)	P (%)	Al (%)	Cu (%)	Mo (%)	V (%)	N (%)	Nb (%)	Cr (%)	Ni (%)
												0.583	21.9	0.226	0.03	0	0.031	0.01	0.206	0.0148	0	0.183	0.06

In this embodiment, the target value M of the mechanical property of the steel plate through replying_TargetFor the UTS of 1512MPa_Target.Due to school Quasi- step A is determined and is corresponded to UTS_TargetFWHM_TargetValue, FWHM_TargetIt is 1.096.It determines and carries out to reach UTS_TargetHeat at The P of reason_Target, it is 14.39.Then, the time t of selection_TargetFor 40 seconds and select T ° of temperature_TargetIt is 650 DEG C.

Therefore, firstly, by test 1 and 2 1200 DEG C at a temperature of heating and hot rolling.The finishing temperature of hot rolling is set as It 890 DEG C and is batched at 400 DEG C after hot rolling.Then, the first cold rolling is realized with 50% cold rolling reduction ratio.This Afterwards, recrystallization annealing is carried out at 825 DEG C during 180 seconds.UTS obtained_{Recrystallization}Value be 980MPa.Then, second is cold It rolls and is realized with 30% cold rolling reduction ratio.UTS obtained_{Cold rolling}Value be 1540MPa.

Then, it anneals at 650 DEG C to test 1 during 40 seconds according to the present invention.After the annealing, to test 1 is replied.The UTS of test 1 is 1512.5MPa.

It anneals, i.e., does not consider through determination according to the method for the present invention to test 2 at 650 DEG C during 90 seconds t_TargetWith T °_Target.After the annealing, test 2 is recrystallized.The UTS of test 2 is 1415.15MPa.The FMHM of trial target 2 is 0.989 and P is 14.12, i.e., except the scope of the present invention.

The result shows that when applying the method according to the invention, being replied with expected mechanical property can be obtained Steel plate.

Claims

1. a kind of method for manufacturing the steel plate through replying with austenitic matrix, the steel plate show to be equal to or more than Target value M_TargetAt least one mechanical property (M), the composition of the steel plate includes by weight:

0.1% < C < 1.2%,

13.0%≤Mn < 25.0%,

S≤0.030%,

P≤0.080%,

N≤0.1%,

Si≤3.0%,

And on the basis of entirely optional, one or more of elements such as below

Nb≤0.5%,

B≤0.005%,

Cr≤1.0%,

Mo≤0.40%,

Ni≤1.0%,

Cu≤5.0%,

Ti≤0.5%,

V≤2.5%,

Al≤4.0%,

The remainder of the composition is constituted by iron and by the inevitable impurity that exploitation generates,

Such method includes being step below:

A. calibration steps, in which:

I. prepare have been subjected to 400 DEG C to 900 DEG C the heat treatment during 40 seconds to 60 minutes the steel at least two sample Product, the heat treatment correspond to Pareq value P,

II. X-ray diffraction is carried out to obtain the spectrum including main peak to the sample, measures the main peak in width at half height FWHM,

III. the M of such sample is measured,

IV. the reply or recrystallization state of each sample are measured,

V. song of the M as the function of FWMH is drawn in the region that the wherein sample is returned to 100% but does not recrystallize from 0 Line,

B. step is calculated, in which:

I. it determines and corresponds to the M_TargetFWHM_TargetValue,

II. it determines and carries out to reach such M_TargetThe heat treatment the pareq value P_Target, and

III. selection corresponds to the P_TargetThe time t of value_TargetWith T ° of temperature_Target,

C. there is M_{Recrystallization}Recrystallization steel plate offer step,

D. in order to obtain with M_{Cold rolling}Steel plate cold rolling step, and

2. according to the method described in claim 1, wherein the steel plate occurs after 700 DEG C to 900 DEG C realization recrystallization annealing Recrystallization.

3. method according to claim 1 or 2, wherein the cold rolling is realized with 1% to 50% reduction ratio.

4. according to the method in any one of claims 1 to 3, wherein in the calibration steps A.II) during, half eminence The measured main peak of width FWHM correspond to Miller indices [311].

5. method according to claim 1 to 4, wherein M is ultimate tensile strength (UTS), breaking elongation (TE) or both (UTS*TE).

6. according to the method described in claim 5, realized using following formula wherein when M is UTS and calculate step B.I) during The determination of FWHM:

UTS_Target=UTS_{Cold bundle}-(UTS_{Cold rolling}-UTS_{Recrystallization}) * (exp ((- FWHM+2.3)/2.3) -1)⁴)。

7. method according to claim 5 or 6, wherein when the M is UTS, the UTS_TargetIt is greater than or equal to 1430MPa。

8. according to the method described in claim 7, the wherein UTS_TargetFor 1430MPa to 2000MPa.

9. according to the method described in claim 5, realized using following formula wherein when M is TE and calculate step B.I) during The determination of FWHM:

TE_Target=TE_{Cold bundle}-(TE_{Recrystallization}-UTS_{Cold bundle}) * (exp ((- FWHM+2.3)/2.3) -1)^2.5)。

10. the method according to any one of claim 5 or 9, wherein when M is TE, TE_TargetMore than or equal to 15%.

11. according to the method described in claim 10, wherein TE_TargetIt is 15% to 30%.

12. according to the method described in claim 5, realized using following formula wherein when M is TE*UTS and calculate step B.I) during FWHM determination:

UTS_Target* TE_Target=100000* (1-0.5FWHM).

13. method according to any one of claim 1 to 12, wherein when M is TE*UTS, UTS_Target*TE_TargetIt is greater than 21000, TE_TargetIt is up to 30%.

14. according to the method for claim 13, wherein UTS_Target*TE_TargetIt is 21000 to 60000, TE_TargetIt is up to 30%.

15. according to claim 1 to method described in any one of 14, wherein FWHM_TargetMore than or equal to 1.0 °.

16. according to the method for claim 15, wherein FWHM_TargetIt is 1.0 ° to 1.5 °.

17. according to claim 1 to method described in any one of 16, wherein P_TargetGreater than 14.2.

18. according to the method for claim 17, wherein P_TargetIt is 14.2 to 25.

19. according to the method for claim 18, wherein P_TargetIt is 14.2 to 18.

20. according to the method for claim 19, wherein T °_TargetIt is 400 DEG C to 900 DEG C, t_TargetIt is 40 seconds to 60 minutes.

21. one kind can be as according to claim 1 to the warp with austenitic matrix that method described in any one of 20 obtains The TWIP steel plate of reply.